1. Field of the Invention
The present invention relates to an isotropic antenna system and a notebook computer adopting the same.
2. Description of the Related Art
In general, an antenna is necessarily provided to a portable notebook computer having a wireless communication function. Thus, a conventional dipole antenna is fixedly or detachably installed at the notebook computer. That is, as shown in FIG. 1, an antenna 12 is installed at a main body 11 of a notebook computer 10 to enable wireless communication. Also, the antenna 12 can be detached from the main body 11 and kept separately, as necessary, when the notebook is carried to another place and the antenna 12 is inconvenient. The antenna 12 emits electric waves into space by receiving an RF signal from a predetermined RF circuit module, which is for one-to-one communication between designated ports. Thus, the antenna 12 installed at the main body 11 hardly needs to have an isotropic property (i.e., that transmitting/receiving sensitivity is uniform in all directions), but needs only a degree of alignment to an access point and a particular port.
Meanwhile, active studies have been underway with the goal of realizing a so-called BLUETOOTH networking for connecting general desktop PCs, notebook PCs, printers, mobile phones and servers by near wireless communications. To realize the BLUETOOTH networking, each apparatus should be provided with an antenna and the antenna should be isotropic. That is, the uniform transmitting/receiving sensitivity should be maintained in all directions regardless of a position.
However, in the case of a notebook computer as shown in FIG. 1, when an LCD case 13 is open in the main body 1, radio waves are blocked by the LCD case 13 so that communication sensitivity with respect to the side opposite of the LCD case 13 is lowered. In particular, since the LCD case 13 is mostly metal-plated to shield against EMI (electromagnetic interference), the communication sensitivity is further degraded.
Also, a typical antenna for wireless communications such as the antenna 12 uses vertically polarized waves. When, the notebook computer 10 is carried by being vertically kept in a case, the vertically polarized waves are not received so that communications may be stopped.
Such a problem can be seen in detail through experiments of a gain pattern of an antenna. FIGS. 2A through 2C are graphs showing the results of experiments of a gain pattern of an antenna when the antenna 12 is installed at one side of the main body 11 and the LCD case 13 is open. FIGS. 3A through 3C are graphs showing the results of experiments of a gain patten of an antenna when the antenna is installed at the LCD case 13. Here, in the drawings, L denotes the length of a dipole antenna, and f denotes the frequency of the electromagnetic waves. That is, comparing FIGS. 2A through 2C with FIGS. 3A through 3C, it can be seen that the difference in the gain pattern of the antenna becomes wider according to the installation position of the antenna. Also, it can be seen that the difference in the gain pattern of the antenna becomes much wider according to the opening/closing state of the LCD case. Thus, an antenna system which can obtain a uniform gain pattern of an antenna in all directions regardless of opening of the LCD case is needed.
To solve the above problem, it is an objective of the present invention to provide an antenna system which is improved to have an isotropic property by having a plurality of antennas, and a notebook computer adopting the same.
Accordingly, to achieve the above objective, there is provided an isotropic antenna system comprising a first antenna for transmitting and receiving electric waves when a cover member installed to be capable of being open or closed with respect to a main body is open, a second antenna for transmitting/receiving electric waves when the cover member is closed, and a switch for selectively switching at least one of the first and second antennas to a predetermined RF circuit module according to the opening or closing of the cover member.
It is preferred in the present invention that the isotropic antenna system further comprises a sensor installed at the main body or cover member for detecting information on the opening/closing of the cover member, and a controlling portion for controlling a connection state of the switch with respect to the first and second antennas according to the information on the opening/closing of the cover member output from the sensor.
Also, it is preferred in the present invention that the isotropic antenna system further comprises a switch button capable of elastically protruding or retreating as the cover member is open or closed so that the first antenna or the second antenna can be connected to the switch.
Also, to achieve another aspect of the above objective, there is provided a notebook computer comprising a computer main body in which an input device is installed, a display member, installed at the computer main body to be capable of being opened or closed, for displaying an image, a first antenna, installed at the display member, for transmitting/receiving electric waves, a second antenna, installed at the computer main body or the display member, for transmitting/receiving electric waves, and a switch for selectively switching at least one of the first and second antennas to a predetermined RF circuit module according to the opening or closing of the cover member, wherein the electric waves can be transmitted/received through at least one antenna regardless of the opening/closing of the display member.